1. Field of the Invention
The invention relates to a buck converter, a triggering method, and a use of the buck converter.
2. Description of the Related Art
Power supplies, in particular switching power supplies and switched mode power supplies as well as primarily and secondarily clocked switching controllers are known from [1]. Every electrical power consuming component requires a supply of electrical power, which is provided by a power supply and/or a power pack. Throughout the world, power lines are used as transmission lines in order to supply current and voltage to a virtually limitless array of electrical devices via electrical outlets. To this end, standardized alternating currents, e.g. 120 volts in the USA and 230 volts in Germany, are customarily supplied via the power lines.
In power factor correction, power consuming components in the circuit, in particular capacitances and inductances of a circuit, are compensated for through an appropriate wiring. Capacitances and inductances are provided, which act in opposition to the capacitive and inductive components of the circuit, thus largely compensating for them. With regard to the topic of power factor correction, the reader is referred to power factor correction at www.tpub.com/neets/book2/4k.htm, for example.
A power supply, e.g. a switched mode power supply, with a nonlinear load characteristic generates current harmonics, even when fed by a purely sinusoidal supply voltage. The line impedance generates harmonics that influence the line voltage and can lead to malfunctions. With regard to CE conformity labeling, it is necessary to test whether the products comply with the requirements of the EMC law. Guidelines related to this classify both the permissible degree of electromagnetic interference emission and the resistance to malfunction in the presence of electromagnetic interference. The permissible limit values and measurement procedures for current harmonics are set forth in the standard EN61000-3-2(also see EMV—Messtechnik [EMC Metrology]: “Gegen Störungen aus dem Netz—Erfüllen Ihre Produkte die EN61000-3-2/-3?” [Preventing Interferences From the Power Grid—Do Your Products Comply with EN61000-3-2/-3?], Endress +Hauser eA, pp. eA 29, on the Internet at: www.zes.com/download/zes_sys6lk_presse_ea—8—01.pdf.
The object of the invention is to disclose a buck converter that essentially conforms to the above-mentioned EN61000-3-2, and is efficient particularly with regard to the power factor correction. The present invention also discloses a triggering method and several uses of the buck converter.
This object is attained according to the defining characteristics of the independent claims. Modifications of the invention are disclosed in the dependent claims.
In order to attain the object of the invention, a buck converter is disclosed, which is equipped with a switch, a diode, an inductance, a capacitor, an input with a first connection and second connection, and an output with a first connection and second connection. The first connection of the input is connected to the first connection of the output via a series circuit comprised of the switch and the inductance; in particular, the switch is provided on the input side and the inductance is provided on the output side. In addition, the cathode of the diode is connected to the connection between the switch and the inductance while the anode of the diode is connected to the second connection of the input and to the second connection of the output. The capacitor is connected in parallel with the connections of the output. The switch can be triggered by combining a first signal with a second signal.
It is thus advantageous that a combination or concatenation of the first signal and the second signal is used to trigger the switch. Because two different signals or information sources are used, the circuit (the buck converter) not only operates efficiently, i.e. provides an efficient power factor correction, but also contains the harmonic amplitudes in accordance with the standard EN61000-3-2.
In one modification, the first connection of the input is a positive connection and the second connection of the input is a negative connection. It is also possible for the first connection of the output to be a positive connection and for the second connection of the output to be a negative connection.
In a preferred embodiment, the polarities of the connections of the input are reversed. In this case, the connections of the cathode and anode of the diode are reversed and in particular, the polarity of the switch is reversed.
According to one embodiment, it is possible to trigger the switch by combining the first signal with the second signal and a third signal. In particular, the third signal can be a control variable from the output of the buck converter. The third signal can also be used to adjust the output signal of the buck converter. In addition, the third signal can be a signal that is constant or that varies in an essentially slow fashion. Preferably, the third signal can be adjusted and/or regulated by means of predetermined or predeterminable parameters. At least one of the following parameters or arbitrary combinations of the following parameters can be used: output voltage of the buck converter, output current of the buck converter, or power of the buck converter.
According to one modification, the switch is comprised of at least one electronic switch.
In another modification, the diode is embodied in the form of an electronic switch. In particular, in order to replace the diode with a MOSFET, it is possible to reduce the switching losses, particularly during an overload operation of the buck converter.
In particular, it is possible to replace the electronic switch with at least one (bipolar) transistor, a field effect transistor, a MOSFET, a thyristor, or an IGBT. It is also possible for combinations of the above-mentioned components to be used as one or more electronic switches.
In one embodiment, the above-mentioned combining of the first signal with the second signal is an overlaying or addition of the two signals.
In one modification, the sum of the first signal and the second signal is compared to the third signal.
The first signal can be a current signal that corresponds in particular to the current flowing through the inductance or through the electronic switch. The current signal can optionally be predetermined or determined by the inductance. In this case, the triggering of the (electronic) switch is influenced by the current of the inductance. To that end, it is possible, for example, for an auxiliary winding of the inductance to be provided, whose signal (current and/or voltage flowing through the auxiliary winding) is evaluated for purposes of triggering the switch.
It is also possible for the current signal to be determined through an integration of a sum based on a voltage in the inductance.
In one modification, the second signal is an essentially triangular signal or an essentially saw tooth-shaped signal. In particular, this essentially triangular or essentially shaped-shaped signal can be generated or predetermined by a generator, in particular a saw tooth generator.
In another modification, the addition of the current signal and the essentially triangular or essentially shaped-shaped signal can be established through an integration of a voltage in the inductance and another voltage. The additional voltage can be determined using a peak value rectification of the voltage in the inductance. It is also possible for the peak value rectification to be carried out with a retention time constant that is in particular (significantly) greater than the line period (e.g. by a factor of 5).
In another modification, an additional peak value rectification is provided, which has a time constant that is in particular (significantly) less than the line period (e.g. by a factor of ⅕).
In addition, it is possible to limit the switch-on duration of the switch, e.g. if the voltage in the inductance falls below a predetermined minimum.
In one modification, the capacitor is an electrolytic capacitor. In this case, its positive pole is connected to the first connection of the output.
The inductance can be embodied in the form of a coil, in particular a throttle.
It is also possible for a rectifier circuit to precede the buck converter.
It is also possible for the buck converter to be used in a power supply, particularly in a power pack or a switched mode power supply. It is also possible for the power supply to be mounted on a mounting rail and/or in a switching cabinet.
A method for triggering the buck converter is also disclosed in order to attain the above-mentioned object of the invention.
The buck converter can also be used for limiting switch-on current and/or for masking or suppressing transients.
It should be noted here that the term overvoltage is intended herein to apply to all forms of voltages greater than a predetermined supply voltage, in particular a line voltage, and all forms of voltage spikes. In particular, the term “transient” is intended herein to apply to all types of chronologically limited overvoltages that deviate from the target values of the electrical supply voltage. It should additionally be noted that an overvoltage can also result from a current spike.
The buck converter can be operated in a single phase network and/or in a three-phase network.
The buck converter is particularly suitable for use in power factor correction.